水稻ERF转录因子家族IX亚组成员在抗病性中的功能及其作用机制

Transcriptional factors, e.g. WRKYs, ERFs and others, play central roles in regulating coordinate expression of a large set of defense genes in plant immune responses against infection of different pathogens. Our previous studies have shown that differential expression of group IX members in the rice ERF tanscriptional facotr family can be induced by pathogen infection and we also found that one member of this group has important function in regulation of rice denfense response. In the present proposal, we will focus on the function and mechanims of all 18 members in this important group of the ERF family in rice disease resistance using molecular, functional genomics and biochemical approaches. Stable transgenic rice lines with overexpression (OE), RNAi-mediated knockdown (RNAi) or chemric suppression (SRDX) for each member of the group IX will be generated and analyzed for their phenotypes against Magnaporthe grisea, Xanthomonas oryzae pv. oryzae, Rhizoctonia solani and different viruses, the causal agents of rice blast, leaf blight, sheath blight and viral diseases, respectively. Once clear phenotype and fucntion for members of the group IX were idnetified, molecular and physiological mechanisms will be analyzed by comparison of changes in contents of resistance-related signaling molecules (e.g. salicylic acid and jasmonic acid) and defense responses (e.g. PR gene expression and cell wall inforcement) among the OE, RNAi and SRDX transgenic lines. Biochemical acitivity, cellular localization and expression patterns of the members with clear phenotypes will be also studied. Expression profiling will be carried out and compared among the OE. RNAi and SRDX lines for the members with clear phenotypes to identify possible candidate targets, whose expression is regulated by the IX member(s), and the function of these ERF IX member-regulated target genes in disease resistance will be also analyzed. Results from this proposed project will be helpful in clarifying the biological functions and mechanism of the group IX members of the ERF family in disease resistance as well as in elucidating the molecular mechanism of rice immune response against different pathogens. The possible group IX member with function in disease resistance identified in this project can be used as useful canadidate genes in generation of novel germplasm resources with improved disease resistance character through genetic engineering approach.

植物对不同病原菌侵染的抗病反应通常需激活大批基因的协同表达，涉及WRKY、ERF等各类转录因子的参与。前期研究中，我们发现水稻ERF类转录因子IX（OsERF-IX）组的一些成员在病菌侵染或非生物逆境胁迫中存在差别表达，其中1个成员直接参与抗病反应。本项目重点研究OsERF-IX组成员在水稻抗病性中的功能及其作用机理。将构建过量表达OE、基因沉默RNAi和嵌合抑制子SRDX转基因株系，比较野生型和三类转基因株系对稻瘟病、白叶枯病、纹枯病或病毒病等不同类型病害的表型变化，分析抗病相关激素含量和抗病反应的分子和生理机制，明确抗病相关OsERF-IX组成员的转录因子活性和细胞定位以及基因表达模式，运用基因芯片表达谱分析分离鉴定其下游靶标基因及其功能。研究结果有助于揭示OsERF-IX组成员在抗病性中的功能及其作用机制，有助于阐明水稻抗病反应的分子调控机理，为创制转基因抗病水稻新种质提供基因资源。

围绕转录因子在植物免疫反应中的调控作用及其机制，本项目重点研究了水稻ERF家族B3亚组OsBIERF3、NAC家族3个基因以及拟南芥和番茄中ERF基因的抗病抗逆功能。OsBIERF3的表达在水稻-稻瘟病菌/白叶枯病菌间的非亲和性互作中显著上调。OsBIERF3-OE植株上稻瘟病和白叶枯病发病显著下降，而OsBIERF3-RNAi株系上发病显著加重。同时OsBIERF3-OE株系提高了稻飞虱抗性，而OsBIERF3-RNAi株系则降低了稻飞虱抗性。OsBIERF3-OE植株中SA、JA和ABA含量高于野生型，而OsBIERF3-RNAi#29植株中SA含量低于野生型、JA含量与野生型无显著变化、而ABA含量高于野生型。OsBIERF3-OE株系细胞壁显著增厚，与细胞壁合成相关基因表达显著上调。接种稻瘟病菌后，OsBIERF3-OE植株中防卫基因表达水平显著高于野生型，而OsBIERF3-RNAi植株中防卫基因表达水平显著低于野生型。结果证明，OsBIERF3正调控对稻瘟病、白叶枯和稻飞虱的抗性反应，可能涉及通过SA和JA信号途径调控防卫基因表达和细胞壁抗性反应等方面。MNAC1在水稻-稻瘟病菌非亲和互作中表现出差别表达特征，并受 SA 和 JA 诱导表达。MNAC1定位于细胞核，并具有转录激活性。MNAC1-OE株系降低了对稻瘟病的抗病性，但不影响对白叶枯病的抗性。MNAC1-OE植株中稻瘟病菌侵染诱导的SA 和 JA积累受到抑制，而且抗病信号途径基因和防卫反应基因的表达也受到抑制。因此，水稻MNAC1负调控对稻瘟病的抗病性，但不影响对白叶枯的抗性，其机制可能与MNAC1对SA和JA信号途径的负调控有关。.此外，研究证明水稻ONAC022是一个逆境胁迫应答基因，并通过ABA介导的信号途径在干旱和盐害胁迫反应中起正调控作用；ONAC095在水稻干旱和冷害胁迫反应中起相反的作用，正调控干旱反应，而负调控冷害反应；拟南芥AtERF15正调控拟南芥中对不同病菌的免疫反应，而AtERF014在拟南芥对不同病菌的免疫反应中起不同的作用；番茄ERF家族B3亚组成员SlERF.A1、SlERF.A3、SlERF.B4和SlERF.C3作为正调控因子参与对灰霉病的免疫反应。.发表标注本项目编号的SCI论文12篇；本项目实施期间培养博士生4名，硕士生5名。